1. Technical Field
The present invention relates generally to multivariable systems and, more particularly, to a system and method that compensates for changes in operating conditions of a multivariable system.
2. Background Information
A gas turbine power system can include a control system, a gas turbine engine having a plurality of engine actuators, and a plurality of engine sensors. The control system controls the engine by generating and providing effector signals to the engine actuators. The term “effector signal” is used herein to describe a command signal that controls operation of the engine through the engine actuators.
The effector signals can be generated by processing goals, limits and a basepoint estimate using a control algorithm such that at least some of the goals are satisfied, subject to each limit being held (i.e., no limit is violated). An example of a goal is to operate the engine at a certain thrust level. An example of a limit (i.e., a maximum or minimum) is to prevent an engine component or system from exceeding a certain temperature. A limit is “active” when its limit value has been met; e.g., when a temperature of a component is, or is predicted to be, at or above a maximum limit temperature. A basepoint estimate is a set of goal and limit values that correspond to an equilibrium point at which each active limit is held and at least some of the goals are satisfied.
During operation, the engine may experience various real-time changes in its system parameters. Changes in the system parameters can result from updated control signals, changes in environmental conditions and changes in operating conditions. Such changes can create discrepancies between engine parameters predicted by the control algorithm and corresponding engine parameters measured by the engine sensors, which in turn can create error in the estimated basepoint.
A typical engine controller can compensate for discrepancies between predicted and measured engine parameters by determining basepoint error and correcting the next basepoint estimate as a function of the basepoint error. The basepoint error can be determined as a function of the goals, inequality limit equations derived from the limits, and equality basepoint equations generated by a basepoint estimator. Determining the basepoint error as a function of the goals, limit equations and basepoint equations, however, can significantly complicate a series of matrix algebra operations performed by the control algorithm. In particular, the control algorithm must perform matrix algebra operations on both (i) the goals and the limit equations to generate the effector signals, and (ii) the basepoint equations to determine basepoint error.
There is a need in the art, therefore, for an control system that can at least partially compensate for engine modeling errors and/or changes in engine operating conditions, while also reducing the amount of matrix algebra operations performed.